1. Field of the invention The present invention relates generally to aircraft rotors, and more particularly to a hub suitable for use with a tilt rotor aircraft.
2. Description of the Prior Art
Design of rotors and propellers for aircraft is often extremely complex. A large number of factors must be taken into account, including flexure of the rotor under heavy loads and the required motions of the rotor blades with respect to the drive mechanism. The considerations for prop rotors, used as both propellers and rotors in aircraft such as a tiltrotor aircraft, can be more complex than usual.
Constant velocity joints must be provided between the rotor shaft and the blades, giving rise to a relatively complex assembly at the hub of the rotor shaft. An example of such an assembly, useful for certain helicopter designs, is described in U.S. Pat. No. 4,729,753. As illustrated therein, numerous approaches to making helicopter and prop rotor assemblies have been tried. Many of these are suitable for a given application, but not for others. As aircraft designs progress, the hub assemblies used on their rotors must meet new specifications which render older designs unsuitable.
The advent of the tilt rotor aircraft has added performance requirements to the hub assembly, resulting from the more complex operation of the craft. The prop systems on a tilt rotor are very large by comparison with standard aircraft, and size becomes an issue. In some designs of a tilt rotor aircraft, particularly suitable for use in light and medium duty models, certain design choices must be made in order that there is simply room for all of the required parts.
Standard rotor hub designs are relatively large, influencing the design of mechanical systems associated with the rotor. For example, a large rotor hub requires a relatively long mast. The hub itself is heavy, and associated systems, such as the control rods, are relatively long and heavy. Systems must be designed so that the control system is not interfered with.
Therefore, it would be desirable to provide a rotor hub design which is suitable for use with the design constraints of a prop rotor aircraft. Such hub must provide proper support for the blades while remaining small compared to prior art designs. A thinner hub design would shorten the mast, lower the height of the associated systems, and save weight.